Vibrational Internal Energy of Chloromethyl Radical Formed by the Photodissociation of CH<sub>2</sub>BrCl at 265 nm

Abstract

Photodissociation of CH 2 BrCl was investigated around 265 nm using resonance-enhanced multiphoton ionization technique combined with velocity map ion-imaging detection.The ion images of Br(2 P 1/2)and Br(2 P 3/2)were analyzed to obtain the corresponding velocity distributions and total translational energy distributions.Using an impulsive model invoking angular momentum conservation,the vibrational internal energy distributions of chloromethyl radical(·CH 2 Cl)formed by the photodissociation of CH 2 BrCl,were derived from the total translational energy distributions.In the CH 2 BrCl+hv→Br(2 P 1/2)+CH 2 Cl channel,v 4,v 3+ v 4,v 2+ v 4 and v 2+ v 6 vibrational modes were found to be excited in the radical;while in the CH 2 BrCl+hv→ Br(2 P 3/2)+CH 2 Cl channel,the excited vibrational modes were v 2 +v 6,v 1 +v 3,v 2 +v 5,v 2 +v 3 +v 5,and v 1 +v 5.The results further implied that,following absorption of one photon by the parent molecule CH 2 BrCl,other vibrational modes besides v 5(CBr stretch)mode,such as v 7(CH 2 a-stretch)mode,are excited in the parent molecule.